The present invention relates to a crawler belt type traveling system adapted for use mainly in construction machines such as crawler dump trucks and hydraulic shovels or in agricultural machinery.
There have been conventionally used construction machine vehicles and agricultural machine vehicles, which are equipped with a crawler belt type traveling system, the system comprising crawler belts made from an elastic material such as rubber for improving ride qualities and reducing noise during traveling. Such a crawler belt type traveling system includes a pair of right and left driving sprockets which are positioned on either the front or rear end of the structure underneath the vehicle. The other end is provided with a pair of right and left idlers. Generally, the right and left sides of the vehicle are respectively provided with a crawler belt which is endlessly wound around each set of the driving sprocket and the idler at their peripheries and the intermediate portion of each crawler belt is supported by a plurality of freely rotatable road wheels.
As shown in FIG. 8 which is a partial cross sectional view illustrating the relationship between a conventional crawler belt and a road wheel, a known crawler belt 100 employed in such a crawler belt type traveling system has a structure in which a crawler belt body 101 is formed in an endless fashion from rubber or an elastic material having rubber qualities and a number of core bars are embedded and aligned at specified intervals within the crawler belt body 101 in a longitudinal direction thereof. Each core bar 102 has, at the center with respect to its widthwise direction, a pair of guide projections 103 which project from the inner circumferential surface of the crawler belt (i.e., the surface opposite to the tread). Provided on the outer right and left sides of the pair of guide projections 103 are road wheel rolling contact sections 104 with which roller sections 111 of each road wheel 110 mounted on the vehicle body are respectively in contact. A shallow groove 105 is formed in an abutting part between each guide projection 103 of the core bar 102 and its associated road wheel rolling contact section 104 such that elastic deformation caused by rolling pressure and exerted on the road wheel rolling contact section 104 is prevented from directly affecting the abutting part. For easy bending of the crawler belt 100, there are formed grooves (not shown) each of which extends in a widthwise direction of the crawler belt 100, being positioned in the space between the adjacent core bars 102 embedded so as to be aligned at specified intervals in the longitudinal direction of the crawler belt 100.
When the vehicle travels on the unleveled ground with such crawler belts 100 while performing its operation, it often rides on stones etc. because of the irregular treads of the road wheels, so that a load is imposed on either the right or left side of the crawler belts with respect to the widthwise direction of the crawler belts. If a load is repeatedly imposed on one side, an excessive pressing force is locally exerted upon the road wheel rolling contact sections 104 on which the road wheels 110 (consisting of a plurality of crawler belt supporting rollers) roll, the road wheels 110 supporting the crawler belts from inside at the intermediate portion thereof This causes immoderate external force working on the abutting part between each road wheel rolling contact section 104 and a side of each guide projection 103 of the core bars 102 adjacent to the road wheel rolling contact section 104.
If such an undesirable situation repeatedly occurs, cracks are generated around the boundary between each guide projection 103 and the crawler belt body 101 owing to the local pressing force working on the road wheel rolling contact sections 104 of the crawler belt body 101. Once cracking occurs, peeling of the elastic material such as rubber develops from the cracked part, resulting in breakage of the crawler belt at the early stage.
As seen from FIG. 8, the above phenomenon is supposed to be caused for the following reason: As the road wheels 110 roll near the root parts of the guide projections 103 of the core bars 102, an excessive pressing force is generated, working on the portions where the elastic material (e.g., rubber) of the crawler belt body 101 is adhered to the side face of the guide projection 103 of each core bar 102 so that a load, which exceeds the shearing stress of the adhesive layer and the limit of the elasticity of the elastic material (e.g., rubber), is repeatedly exerted.
The present invention is directed to overcoming the above problem and a prime object of the invention is therefore to provide a crawler belt type traveling system having crawler belts of improved durability.
The above object can be achieved by a crawler belt type traveling system according to a first aspect of the invention comprising:
crawler belts formed from an elastic material, each crawler belt having core bars embedded therein so as to be aligned at specified intervals in a longitudinal direction of the crawler belt, the core bars each having a pair of guide projections at the center thereof with respect to a widthwise direction of the crawler belt, the pair of guide projections being aligned in a widthwise direction of the crawler belt, and
road wheels each attached to a vehicle body so as to come into rolling contact with a portion outside the pair of guide projections,
wherein each road wheel rolls on road wheel rolling contact sections of each crawler belt with its tread being away from the crawler belt side of a root part of each guide projection.
According to the invention, the tread of each road wheel, which is in contact with road wheel rolling contact sections of a crawler belt to support and press the crawler belt against the ground for running it during traveling, rolls in a position away from the root parts of the guide projections of each core bar. This arrangement can alleviate the undesirable situation in which the elastic deformation of the road wheel rolling contact sections caused by the road wheels concentrates upon the root parts of the guide projections, so that cracking and peeling in the adhesive regions are unlikely to occur, resulting in improved durability of the crawler belts.
The traveling system of the first aspect may be designed such that the guide projection sides of the periphery of each road wheel are formed into a step-like shape so as to be apart from the root parts of the guide projection (a second aspect of the invention). In addition, the guide projection sides of each road wheel may be inclined at an angle greater than the inclination angle of the guide projections (a third aspect of the invention). With these arrangements, even if a roller section of a road wheel is offset to a guide projection side, the tread part does not come into contact with the root part of the guide projection so that an unfavorable situation can be avoided in which a load is concentrated on the regions of the road wheel rolling contact sections in the neighborhood of the root parts of the guide projections, interrupting the operation of the crawler belt which results in breakage of the crawler belt.
The traveling system of the first aspect may be modified such that the portions of each crawler belt close to the root parts of the guide projections are respectively provided with a recess which is larger than the volume of elastic deformation caused by the maximum vehicle body load which acts via the road wheel rolling contact sections (a fourth aspect of the invention). With this arrangement, even if a load is locally imposed on the road wheel rolling contact sections by the road wheels, the recesses absorb the distortion caused by the elastic deformation of the road wheel rolling contact sections (i.e., the distortion is accommodated in the recesses) so that a load concentrated on the joint parts where each guide projection joins to the elastic material can be alleviated, preventing damage to the crawler belts.
The traveling systems of the first or fourth aspect of the invention may be modified such that an irregular surface is formed at least in an adhesive interface between the elastic material and the outer surface of each guide projection of each core bar (a fifth aspect of the invention). This increases adhesion in the adhesive surfaces of the crawler belt forming elastic material (e.g., rubber) and the root part of each guide projection, which, in consequence, prevents peeling of the adhesive layer due to a local external force.
According to a sixth aspect of the invention, there is provided a crawler belt type traveling system comprising:
crawler belts formed from an elastic material, each crawler belt having core bars embedded therein so as to be aligned at specified intervals in a longitudinal direction of the crawler belt, the core bars each having a pair of guide projections at the center thereof with respect to a widthwise direction of the crawler belt, the pair of guide projections being aligned in a widthwise direction of the crawler belt, and
road wheels each attached to a vehicle body so as to come into rolling contact with a portion outside the pair of guide projections,
wherein the elastic material of each crawler belt is adhered so as to extend from the crawler belt side of a root part of each guide projection to a position having a specified height along the outer surface of the guide projection, and
wherein the guide projection sides of each road wheel are respectively formed into a step-like shape so as not to come into contact with joint parts where the elastic material joins to a guide projection.
According to the invention, an adhesive area can be increased in the elastic material joint parts where the root part of a guide projection of each core bar in each crawler belt joins to a road wheel rolling contact section of the crawler belt, thereby increasing adhesion. In addition, the area of the elastic material portions in contact with the guide projections can be increased thereby achieving reinforcement, each elastic material portion leading to a road wheel rolling contact section. For conforming to the increased area of the elastic material portions, the guide projection sides of each road wheel are formed into a stepped shape so as not to come into contact with the elastic material joint parts, thereby not only avoiding local concentration of stress, but also increasing adhesion to prevent damage to the elastic material (e.g., rubber) in the neighborhood of the root parts of the guide projections of each core bar, resulting in improved durability. In the above arrangement, more effectiveness can be achieved by providing irregularity to the outer part of the root part of each guide projection, thereby increasing adhesion.